/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.mvc.support;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.ConversionNotSupportedException;
import org.springframework.beans.TypeMismatchException;
import org.springframework.core.Ordered;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.lang.Nullable;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;
import org.springframework.validation.BindException;
import org.springframework.validation.BindingResult;
import org.springframework.web.HttpMediaTypeNotAcceptableException;
import org.springframework.web.HttpMediaTypeNotSupportedException;
import org.springframework.web.HttpRequestMethodNotSupportedException;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.MissingPathVariableException;
import org.springframework.web.bind.MissingServletRequestParameterException;
import org.springframework.web.bind.ServletRequestBindingException;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestPart;
import org.springframework.web.context.request.async.AsyncRequestTimeoutException;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.support.MissingServletRequestPartException;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.NoHandlerFoundException;
import org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

/**
 * The default implementation of the {@link org.springframework.web.servlet.HandlerExceptionResolver}
 * interface, resolving standard Spring MVC exceptions and translating them to corresponding
 * HTTP status codes.
 *
 * <p>This exception resolver is enabled by default in the common Spring
 * {@link org.springframework.web.servlet.DispatcherServlet}.
 *
 * <p>
 * <table>
 * <caption>Supported Exceptions</caption>
 * <thead>
 * <tr>
 * <th class="colFirst">Exception</th>
 * <th class="colLast">HTTP Status Code</th>
 * </tr>
 * </thead>
 * <tbody>
 * <tr class="altColor">
 * <td><p>HttpRequestMethodNotSupportedException</p></td>
 * <td><p>405 (SC_METHOD_NOT_ALLOWED)</p></td>
 * </tr>
 * <tr class="rowColor">
 * <td><p>HttpMediaTypeNotSupportedException</p></td>
 * <td><p>415 (SC_UNSUPPORTED_MEDIA_TYPE)</p></td>
 * </tr>
 * <tr class="altColor">
 * <td><p>HttpMediaTypeNotAcceptableException</p></td>
 * <td><p>406 (SC_NOT_ACCEPTABLE)</p></td>
 * </tr>
 * <tr class="rowColor">
 * <td><p>MissingPathVariableException</p></td>
 * <td><p>500 (SC_INTERNAL_SERVER_ERROR)</p></td>
 * </tr>
 * <tr class="altColor">
 * <td><p>MissingServletRequestParameterException</p></td>
 * <td><p>400 (SC_BAD_REQUEST)</p></td>
 * </tr>
 * <tr class="rowColor">
 * <td><p>ServletRequestBindingException</p></td>
 * <td><p>400 (SC_BAD_REQUEST)</p></td>
 * </tr>
 * <tr class="altColor">
 * <td><p>ConversionNotSupportedException</p></td>
 * <td><p>500 (SC_INTERNAL_SERVER_ERROR)</p></td>
 * </tr>
 * <tr class="rowColor">
 * <td><p>TypeMismatchException</p></td>
 * <td><p>400 (SC_BAD_REQUEST)</p></td>
 * </tr>
 * <tr class="altColor">
 * <td><p>HttpMessageNotReadableException</p></td>
 * <td><p>400 (SC_BAD_REQUEST)</p></td>
 * </tr>
 * <tr class="rowColor">
 * <td><p>HttpMessageNotWritableException</p></td>
 * <td><p>500 (SC_INTERNAL_SERVER_ERROR)</p></td>
 * </tr>
 * <tr class="altColor">
 * <td><p>MethodArgumentNotValidException</p></td>
 * <td><p>400 (SC_BAD_REQUEST)</p></td>
 * </tr>
 * <tr class="rowColor">
 * <td><p>MissingServletRequestPartException</p></td>
 * <td><p>400 (SC_BAD_REQUEST)</p></td>
 * </tr>
 * <tr class="altColor">
 * <td><p>BindException</p></td>
 * <td><p>400 (SC_BAD_REQUEST)</p></td>
 * </tr>
 * <tr class="rowColor">
 * <td><p>NoHandlerFoundException</p></td>
 * <td><p>404 (SC_NOT_FOUND)</p></td>
 * </tr>
 * <tr class="altColor">
 * <td><p>AsyncRequestTimeoutException</p></td>
 * <td><p>503 (SC_SERVICE_UNAVAILABLE)</p></td>
 * </tr>
 * </tbody>
 * </table>
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @see org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler
 * @since 3.0
 */
public class DefaultHandlerExceptionResolver extends AbstractHandlerExceptionResolver {

    /**
     * Log category to use when no mapped handler is found for a request.
     *
     * @see #pageNotFoundLogger
     */
    public static final String PAGE_NOT_FOUND_LOG_CATEGORY = "org.springframework.web.servlet.PageNotFound";

    /**
     * Additional logger to use when no mapped handler is found for a request.
     *
     * @see #PAGE_NOT_FOUND_LOG_CATEGORY
     */
    protected static final Log pageNotFoundLogger = LogFactory.getLog(PAGE_NOT_FOUND_LOG_CATEGORY);


    /**
     * Sets the {@linkplain #setOrder(int) order} to {@link #LOWEST_PRECEDENCE}.
     */
    public DefaultHandlerExceptionResolver() {
        setOrder(Ordered.LOWEST_PRECEDENCE);
        setWarnLogCategory(getClass().getName());
    }


    @Override
    @Nullable
    protected ModelAndView doResolveException(
            HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex) {

        try {
            if (ex instanceof HttpRequestMethodNotSupportedException) {
                return handleHttpRequestMethodNotSupported(
                        (HttpRequestMethodNotSupportedException) ex, request, response, handler);
            }
            else if (ex instanceof HttpMediaTypeNotSupportedException) {
                return handleHttpMediaTypeNotSupported(
                        (HttpMediaTypeNotSupportedException) ex, request, response, handler);
            }
            else if (ex instanceof HttpMediaTypeNotAcceptableException) {
                return handleHttpMediaTypeNotAcceptable(
                        (HttpMediaTypeNotAcceptableException) ex, request, response, handler);
            }
            else if (ex instanceof MissingPathVariableException) {
                return handleMissingPathVariable(
                        (MissingPathVariableException) ex, request, response, handler);
            }
            else if (ex instanceof MissingServletRequestParameterException) {
                return handleMissingServletRequestParameter(
                        (MissingServletRequestParameterException) ex, request, response, handler);
            }
            else if (ex instanceof ServletRequestBindingException) {
                return handleServletRequestBindingException(
                        (ServletRequestBindingException) ex, request, response, handler);
            }
            else if (ex instanceof ConversionNotSupportedException) {
                return handleConversionNotSupported(
                        (ConversionNotSupportedException) ex, request, response, handler);
            }
            else if (ex instanceof TypeMismatchException) {
                return handleTypeMismatch(
                        (TypeMismatchException) ex, request, response, handler);
            }
            else if (ex instanceof HttpMessageNotReadableException) {
                return handleHttpMessageNotReadable(
                        (HttpMessageNotReadableException) ex, request, response, handler);
            }
            else if (ex instanceof HttpMessageNotWritableException) {
                return handleHttpMessageNotWritable(
                        (HttpMessageNotWritableException) ex, request, response, handler);
            }
            else if (ex instanceof MethodArgumentNotValidException) {
                return handleMethodArgumentNotValidException(
                        (MethodArgumentNotValidException) ex, request, response, handler);
            }
            else if (ex instanceof MissingServletRequestPartException) {
                return handleMissingServletRequestPartException(
                        (MissingServletRequestPartException) ex, request, response, handler);
            }
            else if (ex instanceof BindException) {
                return handleBindException((BindException) ex, request, response, handler);
            }
            else if (ex instanceof NoHandlerFoundException) {
                return handleNoHandlerFoundException(
                        (NoHandlerFoundException) ex, request, response, handler);
            }
            else if (ex instanceof AsyncRequestTimeoutException) {
                return handleAsyncRequestTimeoutException(
                        (AsyncRequestTimeoutException) ex, request, response, handler);
            }
        }
        catch (Exception handlerEx) {
            if (logger.isWarnEnabled()) {
                logger.warn("Failure while trying to resolve exception [" + ex.getClass().getName() + "]", handlerEx);
            }
        }
        return null;
    }

    /**
     * Handle the case where no request handler method was found for the particular HTTP request method.
     * <p>The default implementation logs a warning, sends an HTTP 405 error, sets the "Allow" header,
     * and returns an empty {@code ModelAndView}. Alternatively, a fallback view could be chosen,
     * or the HttpRequestMethodNotSupportedException could be rethrown as-is.
     *
     * @param ex       the HttpRequestMethodNotSupportedException to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler, or {@code null} if none chosen
     *                 at the time of the exception (for example, if multipart resolution failed)
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleHttpRequestMethodNotSupported(HttpRequestMethodNotSupportedException ex,
                                                               HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        String[] supportedMethods = ex.getSupportedMethods();
        if (supportedMethods != null) {
            response.setHeader("Allow", StringUtils.arrayToDelimitedString(supportedMethods, ", "));
        }
        response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, ex.getMessage());
        return new ModelAndView();
    }

    /**
     * Handle the case where no {@linkplain org.springframework.http.converter.HttpMessageConverter message converters}
     * were found for the PUT or POSTed content.
     * <p>The default implementation sends an HTTP 415 error, sets the "Accept" header,
     * and returns an empty {@code ModelAndView}. Alternatively, a fallback view could
     * be chosen, or the HttpMediaTypeNotSupportedException could be rethrown as-is.
     *
     * @param ex       the HttpMediaTypeNotSupportedException to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleHttpMediaTypeNotSupported(HttpMediaTypeNotSupportedException ex,
                                                           HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        response.sendError(HttpServletResponse.SC_UNSUPPORTED_MEDIA_TYPE);
        List<MediaType> mediaTypes = ex.getSupportedMediaTypes();
        if (!CollectionUtils.isEmpty(mediaTypes)) {
            response.setHeader("Accept", MediaType.toString(mediaTypes));
        }
        return new ModelAndView();
    }

    /**
     * Handle the case where no {@linkplain org.springframework.http.converter.HttpMessageConverter message converters}
     * were found that were acceptable for the client (expressed via the {@code Accept} header.
     * <p>The default implementation sends an HTTP 406 error and returns an empty {@code ModelAndView}.
     * Alternatively, a fallback view could be chosen, or the HttpMediaTypeNotAcceptableException
     * could be rethrown as-is.
     *
     * @param ex       the HttpMediaTypeNotAcceptableException to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleHttpMediaTypeNotAcceptable(HttpMediaTypeNotAcceptableException ex,
                                                            HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        response.sendError(HttpServletResponse.SC_NOT_ACCEPTABLE);
        return new ModelAndView();
    }

    /**
     * Handle the case when a declared path variable does not match any extracted URI variable.
     * <p>The default implementation sends an HTTP 500 error, and returns an empty {@code ModelAndView}.
     * Alternatively, a fallback view could be chosen, or the MissingPathVariableException
     * could be rethrown as-is.
     *
     * @param ex       the MissingPathVariableException to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     * @since 4.2
     */
    protected ModelAndView handleMissingPathVariable(MissingPathVariableException ex,
                                                     HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex.getMessage());
        return new ModelAndView();
    }

    /**
     * Handle the case when a required parameter is missing.
     * <p>The default implementation sends an HTTP 400 error, and returns an empty {@code ModelAndView}.
     * Alternatively, a fallback view could be chosen, or the MissingServletRequestParameterException
     * could be rethrown as-is.
     *
     * @param ex       the MissingServletRequestParameterException to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleMissingServletRequestParameter(MissingServletRequestParameterException ex,
                                                                HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        response.sendError(HttpServletResponse.SC_BAD_REQUEST, ex.getMessage());
        return new ModelAndView();
    }

    /**
     * Handle the case when an unrecoverable binding exception occurs - e.g. required header, required cookie.
     * <p>The default implementation sends an HTTP 400 error, and returns an empty {@code ModelAndView}.
     * Alternatively, a fallback view could be chosen, or the exception could be rethrown as-is.
     *
     * @param ex       the exception to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleServletRequestBindingException(ServletRequestBindingException ex,
                                                                HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        response.sendError(HttpServletResponse.SC_BAD_REQUEST, ex.getMessage());
        return new ModelAndView();
    }

    /**
     * Handle the case when a {@link org.springframework.web.bind.WebDataBinder} conversion cannot occur.
     * <p>The default implementation sends an HTTP 500 error, and returns an empty {@code ModelAndView}.
     * Alternatively, a fallback view could be chosen, or the ConversionNotSupportedException could be
     * rethrown as-is.
     *
     * @param ex       the ConversionNotSupportedException to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleConversionNotSupported(ConversionNotSupportedException ex,
                                                        HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        sendServerError(ex, request, response);
        return new ModelAndView();
    }

    /**
     * Handle the case when a {@link org.springframework.web.bind.WebDataBinder} conversion error occurs.
     * <p>The default implementation sends an HTTP 400 error, and returns an empty {@code ModelAndView}.
     * Alternatively, a fallback view could be chosen, or the TypeMismatchException could be rethrown as-is.
     *
     * @param ex       the TypeMismatchException to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleTypeMismatch(TypeMismatchException ex,
                                              HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        response.sendError(HttpServletResponse.SC_BAD_REQUEST);
        return new ModelAndView();
    }

    /**
     * Handle the case where a {@linkplain org.springframework.http.converter.HttpMessageConverter message converter}
     * cannot read from a HTTP request.
     * <p>The default implementation sends an HTTP 400 error, and returns an empty {@code ModelAndView}.
     * Alternatively, a fallback view could be chosen, or the HttpMessageNotReadableException could be
     * rethrown as-is.
     *
     * @param ex       the HttpMessageNotReadableException to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleHttpMessageNotReadable(HttpMessageNotReadableException ex,
                                                        HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        response.sendError(HttpServletResponse.SC_BAD_REQUEST);
        return new ModelAndView();
    }

    /**
     * Handle the case where a
     * {@linkplain org.springframework.http.converter.HttpMessageConverter message converter}
     * cannot write to a HTTP request.
     * <p>The default implementation sends an HTTP 500 error, and returns an empty {@code ModelAndView}.
     * Alternatively, a fallback view could be chosen, or the HttpMessageNotWritableException could
     * be rethrown as-is.
     *
     * @param ex       the HttpMessageNotWritableException to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleHttpMessageNotWritable(HttpMessageNotWritableException ex,
                                                        HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        sendServerError(ex, request, response);
        return new ModelAndView();
    }

    /**
     * Handle the case where an argument annotated with {@code @Valid} such as
     * an {@link RequestBody} or {@link RequestPart} argument fails validation.
     * <p>By default, an HTTP 400 error is sent back to the client.
     *
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleMethodArgumentNotValidException(MethodArgumentNotValidException ex,
                                                                 HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        response.sendError(HttpServletResponse.SC_BAD_REQUEST);
        return new ModelAndView();
    }

    /**
     * Handle the case where an {@linkplain RequestPart @RequestPart}, a {@link MultipartFile},
     * or a {@code javax.servlet.http.Part} argument is required but is missing.
     * <p>By default, an HTTP 400 error is sent back to the client.
     *
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleMissingServletRequestPartException(MissingServletRequestPartException ex,
                                                                    HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        response.sendError(HttpServletResponse.SC_BAD_REQUEST, ex.getMessage());
        return new ModelAndView();
    }

    /**
     * Handle the case where an {@linkplain ModelAttribute @ModelAttribute} method
     * argument has binding or validation errors and is not followed by another
     * method argument of type {@link BindingResult}.
     * <p>By default, an HTTP 400 error is sent back to the client.
     *
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     */
    protected ModelAndView handleBindException(BindException ex, HttpServletRequest request,
                                               HttpServletResponse response, @Nullable Object handler) throws IOException {

        response.sendError(HttpServletResponse.SC_BAD_REQUEST);
        return new ModelAndView();
    }

    /**
     * Handle the case where no handler was found during the dispatch.
     * <p>The default implementation sends an HTTP 404 error and returns an empty
     * {@code ModelAndView}. Alternatively, a fallback view could be chosen,
     * or the NoHandlerFoundException could be rethrown as-is.
     *
     * @param ex       the NoHandlerFoundException to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler, or {@code null} if none chosen
     *                 at the time of the exception (for example, if multipart resolution failed)
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     * @since 4.0
     */
    protected ModelAndView handleNoHandlerFoundException(NoHandlerFoundException ex,
                                                         HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        pageNotFoundLogger.warn(ex.getMessage());
        response.sendError(HttpServletResponse.SC_NOT_FOUND);
        return new ModelAndView();
    }

    /**
     * Handle the case where an async request timed out.
     * <p>The default implementation sends an HTTP 503 error.
     *
     * @param ex       the {@link AsyncRequestTimeoutException }to be handled
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler, or {@code null} if none chosen
     *                 at the time of the exception (for example, if multipart resolution failed)
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     * @since 4.2.8
     */
    protected ModelAndView handleAsyncRequestTimeoutException(AsyncRequestTimeoutException ex,
                                                              HttpServletRequest request, HttpServletResponse response, @Nullable Object handler) throws IOException {

        if (!response.isCommitted()) {
            response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
        }
        else {
            logger.warn("Async request timed out");
        }
        return new ModelAndView();
    }

    /**
     * Invoked to send a server error. Sets the status to 500 and also sets the
     * request attribute "javax.servlet.error.exception" to the Exception.
     */
    protected void sendServerError(Exception ex, HttpServletRequest request, HttpServletResponse response)
            throws IOException {

        request.setAttribute("javax.servlet.error.exception", ex);
        response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
    }

}
